Above: A myriad of tunnels are required for the complex upgrade and expansion at EnBW’s Forbach site PHOTO CREDIT: ENBW, ARTIS ULI DECK


With more non-hydro renewables such as wind


and solar comes more variability in generation output, which needs countered in two ways - fill the gaps in generation and do so exceedingly fast; and, help to maintain the operational stability of the grid amidst so much variation, which can for example affect maintenance of electricity frequency. Pumped storage hydropower is a proven solution to quickly satisfy both needs. This form of hydro exploits two bodies of water at sufficiently different elevations, and moves flows between them. It is, in effect, a gravity-charged hydraulic system. The creation of pumped storage hydropower facilities


typically combines mechanical and electrical equipment with major civil engineering infrastructure - often including underground works, which in the case of Forbach are both old and new. Excavations are well underway on the new Forbach


tunnels and more than half of the tunnelling work has been completed.


PROJECT PLAN Feasibility studies began almost 20 years ago, over 2007-9, to allow EnBW to examine options to further develop the Forbach hydro site. Planning followed, considering upper and lower reservoir scenarios, until the owner submitted a planning application for the modernisation, conversion and expansion works in 2018. Planning approval then took five years to achieve,


and was awarded in early 2023 by Karlsruhe Regional Council. The utility’s project manager, Ulrich Gommel, said of


the project milestone at the time, in a statement: “We have worked extensively with the relevant authorities to meet the diverse requirements for a complex construction project of this kind.” Even with approval, as with many other energy


sector projects these days, a final investment decision still needed to be made by the owner, to decide if the particular economic and financial conditions were still suitable to proceed. With such a greenlight,


Above: The project expansion was approved in 2023 and tunnelling got underway across multiple sites from mid-2024 PHOTO PHOTO CREDIT: (LEFT) ENBW (RIGHT) PORR


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